Method for sensing faulty combustion in an internal combustion engine

Claim 1

An improved method of detecting faulty combustion in an internal combustion engine of the type having a plurality of cylinders and a crankshaft carrying a target, wherein a current value of a critical parameter is calculated for each cylinder of the internal combustion engine, on the basis of a linear combination of time intervals between predetermined angular positions of the target; and the critical parameter is compared to a fault threshold obtained experimentally in a reference engine; the improvement which comprises: calculating a current value of the critical parameter for a respective cylinder; determining whether the engine is in a combustion-free operating state and within a speed range centered around a predetermined speed; if the engine is determined to be in the combustion-free operating state and within the given speed range in the determining step, calculating a correction coefficient for the critical parameter relative to the reference engine for the respective cylinder, independently of the predetermined speed, on the basis of the current value of the critical parameter and a reference value obtained under substantially identical conditions in the reference engine; and correcting the values of the critical parameter with the correction coefficient prior to comparing the critical parameter with the fault threshold, and the correcting step being performed with the correction coefficient for all engine speeds at which the critical parameter is calculated.